In late 2011, a young and brash Drew Houston was doing battle with Steve Jobs. Two years shy of 30, the Dropbox cofounder and CEO had brushed aside the advances of the Apple guru only to face him head-to-head when Jobs launched iCloud, a service meant to crush his cloud-based file-sharing company.

Houston's reaction at the time: "Oh sh-t."

Less than three years later, Houston, now 30, looks to have come off a lot stronger from the war. On Friday afternoon, the Wall Street Journal first reported that that Dropbox had closed a $250 million round of funding at a $10 billion valuation. Based on FORBES' calculations, that makes the Dropbox chief Silicon Valley's newest Silicon billionaire.

FORBES estimates that Houston has at least a 10% stake in the San Francisco-based company. In an Oct. 2011 cover story on Houston and Dropbox, FORBES reported that Dropbox's CEO had an estimated 15% stake worth $600 million after the company closed a round at a $4 billion valuation. At least two sources confirmed that Houston was a billionaire following Friday's fundraising round, led by a BlackRock investment fund. At the $10 billion valuation, Houston's stake in the company he cofounded with Arash Ferdowsi, could be worth anywhere from $1 billion to $1.5 billion, depending on how much he still owns.

A spokesperson for Dropbox did not respond to an email request for comment.

Dropbox's last round of investment came in 2011 when it raised $250 million, with investors that included Goldman Sachs, Accel Partners and Sequoia Capital.

BlackRock's investment affirms Dropbox as one of Silicon Valley's most valuable private companies, among the likes of Jack Dorsey's Square and Palo Alto-based data-mining firm Palantir. The deal also helps Houston join an elite group of founders like Mark Zuckerberg, Ev Williams and, most recently, Aneel Bhusri, all of whom have ridden their their tech startups into the realm of 10-figure fortunes.

In reflecting back on his path to founding his company, Houston told FORBES in 2011: “I wanted to live the dream and felt stuck eating Hot Pockets.”

Now a billionaire, Houston can afford a lot more than just Hot Pockets.